The present invention relates to a probe for a scanning type microscope which images a surface structure of a specimen, by using a conductive nanotube as a probe needle. More particularly, the present invention relates to a probe for a conductive scanning type microscope in which a conductive nanotube and a cantilever are electrically connected by coating both of them with a conductive deposit, a conductive film and a conductive coating film, and relates further to a machining method using the same, wherein a voltage can be applied between the conductive nanotube and a specimen so that a current flows.
In order to image a surface structure of a specimen by means of an atomic force microscope abbreviated as AFM, a probe needle is needed which is caused to approach to the surface of the specimen and to obtain information from it. As the probe needle, a cantilever made of silicon or silicon-nitride, which has a protruding portion (or pyramid portion) at the tip end, has been known in the past.
A conventional cantilever is formed by means of the micro-fabrication technique such as lithography, etching, etc. Since the cantilever detects atomic force from the surface of specimen by the tip end of protruding portion, the degree of clearness of an image is determined by the degree of sharpness of the tip end. Then, in the sharpening treatment of the tip end of the protruding portion which serves as a probe needle, an oxide process using a semi-conduction treatment technique and an etching process of an oxide film are utilized. However, there is a lower limit in the reduction of size even in the semi-conductor treatment technique, so that the degree of sharpness of the tip end of the protruding portion above-described is also physically limited.
On the other hand, a carbon nanotube was discovered as a carbon matter having a new structure. The carbon nanotube is from about 1 nm to several 10 nm in diameter and several xcexcm in length, and its aspect ratio is about 100xcx9c1000. It is difficult to form a probe needle of 1 nm diameter by the present technique of semiconductor. Therefore, in this respect, the carbon nanotube provides best condition for the probe needle of the AFM.
In such a situation, H. Dai and others published, in Nature (Vol.384, Nov. 14, 1996), a report with respect to the AMF probe in which a carbon nanotube is stuck on the tip of the protruding portion of a cantilever. Though the probe proposed by them was of epoch-making, the carbon nanotube fell off from the protruding portion during repeatedly scanning surfaces of specimens, since the carbon nanotube was simply stuck on the protruding portion.
In order to solve this weak point, the present inventors have achieved to develop a method fastening firmly the carbon nanotube to the protruding portion of the cantilever. Results of this invention have been published; first fastening method as the publication No.2000-227435, and second fastening method as the publication No.2000-249712.
The first fastening method above-mentioned is that a coating film is formed by means of irradiating an electron beam to the base end portion of a nanotube, and next the nanotube is fastened to the cantilever by means of coating the nanotube with the coating film. The second method is that the base end portion of the nanotube is fusion-fastened to the protruding portion of the cantilever by means of irradiating an electron beam on the base end portion of the nanotube or by means of electrically transmitting it.
As a marketed cantilever, as previously mentioned, is manufactured by means of the semiconductor process-technique, its material is silicon or silicon-nitride. The silicon-nitride is insulator, though the silicon is semi-conductor. It, therefore, was incapable to apply a voltage or to flow current the between the probe needle of the conductive nanotube and a specimen, even if conductive nanotubes such as carbon nanotube, etc. was fastened to the protruding portion of the cantilever, since the cantilever itself had not conductivity.
In a case that a probe has not conductivity, it means that uses of the probe is much limited. For example, the probe can not be used for a scanning tunnel microscope, as the tunnel microscope images a specimen by detecting a tunnel current between the probe needle and the specimen.
Furthermore, by using this probe, it is unable to heap up atoms on the surface of a specimen, to transfer or to take out atoms form the surface of a specimen. In order to process a specimen by means of operating atoms in this manner, it is necessary to apply a voltage to the probe needle. The technique of nano-process is thought as a fundamental technology as well as bio-technology in the 21 century. Hence, the utility of a probe will be much limited in the future, without solving this problem.
Accordingly, an object of the present invention is to realize a probe for a conductive scanning type microscope in which a voltage is applicable and a current can flows between a conductive nanotube and a specimen, by means of electrically connecting cantilever and a probe needle which comprise the conductive nonotube.
The present invention provides, in a probe for a scanning type microscope, by which substance information of a specimen is obtained by means of a tip of a probe needle of a conductive nanotube fastened to a cantilever; a probe for a conductive scanning type microscope characterized in that a conductive nanotube and a conductive film are caused to be electrically transmitted by means of a conductive resolution deposit of organic gas, wherein the probe comprises a conductive films formed on the surface of said cantilever, the conductive nanotube, a base end portion of which is disposed in contact with a specified portion of the surface of the cantilever, and the conductive resolution deposit with which the conductive nanotube is fastened by coating from the base end portion of the conductive nanotube to a part of said conductive films.
The present invention provides, in a probe for a scanning type microscope which obtains substance information of a specimen surface through the tip of a conductive nanotube probe needle fastened to a cantilever; a probe for a conductive scanning type microscope characterized in that a conductive nanotube and a conductive film are caused to be electrically transmitted by means of a conductive deposit, wherein said probe comprises a conductive films formed on the surface of said cantilever, a conductive nanotube, a base end portion of which is disposed in contact with a specified surface portion of this conductive film, and a conductive deposit, with which the base end portion of the conductive nanotube is coated in order to fasten it.
The present invention provides a probe for a conductive scanning microscope described in the first and second parts of the present invention, wherein the conductive state between the conductive nonotube and the cantilever is made accurate by means of furthermore forming a conductive coating film on said conductive deposit, so that the coating film reaches to both the conductive nanotube and the conductive film.
The present invention provides, in a probe for a conductive scanning type microscope which obtains substance information of a surface of a specimen through the tip portion of a conductive nanotube probe needle adhered to a cantilever; a probe for a conductive scanning type microscope which is characterized in that a conductive nanotube and a cantilever are caused to be in a electrically transmitted state, wherein the probe comprises a conductive nanotube, the base end portion of which is disposed in contact with the specified surface portion of said cantilever, a conductive deposit with which a conductive nanotube is fastened to a cantilever by coating the base end portion of it, and a conductive coating film is formed so that it covers this conductive deposit and reaches both the conductive nanotube and the cantilever surface.
The present invention provides a probe for a conductive scanning type microscope described in the third and fourth parts of the present invention, wherein said conductive coating film is formed so that it covers both the tip end and the tip end portion of the nanotube.
The present invention provides a probe for a conductive scanning type microscope described in the fifth part of the present invention, wherein a conductive substance constituting the above described conductive coating film is magnetic substance.
The present invention provides a method to process specimens by means of a probe for a conductive scanning type microscope which is characterized in that by using the probe for the conductive scanning type microscope described in the fifth part of the present invention, the conductive coating film made of a metal film serves as a metal source and by applying a predetermined voltage between this probe for the conductive scanning type microscope and a specimen, metallic atoms included in the metal source are ion-emitted by electric field from the tip of the nanotube to a specimen surface and as the result, and the atoms form a metallic deposit on the surface of the specimen.
The present invention provides a processing method described in the seventh part of the present invention, wherein a diameter of the above-described metallic deposit is 50 nm or less.
The present inventors have earnestly investigated development of conductive scanning type microscopes and have finally achieved an idea of a method to electrically connect a conductive nanotube with a cantilever by a conductive film or by a conductive coating film.
The fundamental structure is that, by preparing a conductive film formed on a cantilever, this conductive film is caused to be electrically connected with a conductive nanotubes by a conductive deposit. In order to make this electric conductivity assured, the structure is employed in that the conductive nanotubes and the conductive film are forced to be electrically connected by means of covering over the conductive deposit with a conductive coating film.
The term so called xe2x80x9cconductive nanotubexe2x80x9d refers the nanotube that possesses electrical conductivity. In general, there are carbon nanotubes, etc. as conductive nanotubes and there are BN series nanotubes, BCN series nanotubes, etc. as insulation nanotubes. However, insulation nanotubes can be transmuted to conductive nanotubes by means of forming conductive films on surfaces of the insulation nanotubes. Conductive nanotubes include the nanotubes that get conductivity by such a processing.
Conductive films formed on cantilevers are, so called, electrically conductive films such as metallic films, carbon films, etc. As the manufacturing method, various methods are able to be utilized such as physical vapor deposition method (PVD) or chemical vapor deposition method (CVD) which include vacuum vapor deposition, ion-plating, spattering, etc., and also such as electric plating, electroless plating, etc. The conductive films thus manufactured have a function as electrodes which is connected with external power supply.
Conductive deposits fastening conductive nanotubes to cantilevers are formed by means of heaping up decomposed-components of organic gases on necessary portions, while decomposing organic gases such as hydrocarbon series gases or organic metallic gases by means of electron beams or ion beams. As for the materials, carbon deposits or metal deposits are used.
In a case where the organic gas is hydrocarbon series gas, the above-described decomposed-deposit is carbon deposit. In general, though carbon deposits comprising graphite substances possess conductivity, deposits comprising amorphous carbons widely distribute with respect to the quality of conductivity, from conductors to insulators, according to thickness of films. Thin films of amorphous carbon are conductive, and thick ones are insulated. Accordingly, by fastening a conductive nanotube to a cantilever with extremely thin films of carbon deposits, the conductivity is caused to be maintained.
In a case where the organic gas is organic metallic gas, the above-described decomposed-deposit forms a metal deposit. This metal deposit, owing to its conductive property, can be utilized as the conductive deposit of the present invention. As metal deposits have conductivity, irrespective of the thickness of metal deposits, metal deposits are more useful than carbon deposits in order to assure conductivity.
As the above-described hydrocarbon series substances, there are hydrocarbons of methane series, hydrocarbons of ethylene series, hydrocarbons of acetylene series, cyclic hydrocarbons, etc.; more concretely saying, hydrocarbons of less molecular weight such as ethylene or acetylene are favorable among them. Furthermore, as the above-described organic metallic gases, the following gases can be utilized; for examples, W(CO)6, Cu(hfac)2, (hfac: hexa-flouro-acetyl-acetonate), (CH3)2AlH, Al(CH2xe2x80x94CH)(CH3)2, [(CH3)3Al]2, (C2H5)3Al, (Ixe2x80x94C4H9)3Al, (CH3)3AlCH3, Ni(CO)4, Fe(CO)4, Cr[C6H5(CH3)2], Mo(CO)6, Pb(C2H5)4, Pb(C5H7O2)2, (C2H5)3PbOCH2C(CH3)2, (CH3)4Sn, (C2H5)4Sn, Nb(OC2H5)5, Ti(i-OC3H7)4, Zr(C11H19O2)4, La(C11H19O2)3, Sr[Ta(OC2H5)6]2, Sr[Ta(OC2H5)5(Oc2H4OcH3)]2, Ba(C11H19O2)2, (Ba,Sr)3(C11H19O2), Pb(C11H19O2)2, Zr(OtC4H9)4, Zr(OiC3H7)(C11H19O2)3, Ti(OiC3H7)2(C11H19O2), Bi(OtC5H11)3, Ta(OC2H5)5, Ta(OiC3H7)5, Nb(OiC3Hxe2x80x2)5, Ge(OC2H5)4, Y(C11H19O2)3, Ru(C11H19O2)3, Ru(C5H4C2H5)2, Ir(C5H4C2H5)(C8H12), Pt(C5H4C2H5)(CH3)3, Ti[N(CH3)2]4, Ti[N(C2H5)2]4, As(OC2H5)3, B(OC2H3)3, Ca(OCH3)2, Ce(OCxe2x80x3H5)3, Co(OiC3H7)2, Dy(OiC3H7)2, Er(OiC3H7)2, Eu(OiC3H7)2, Fe(OCH3)3, Ga(OCH3)3, Gd(OiC3H7)3, Hf(OCH3)4, In(OCH3)3, KOCH3, LiOCH3, Mg(OCH3)2, Mn(OiC3H7)2, NaOCH3, Nd(OiC3H7)3, Po(OCH3)3, Pr(OiC3H7)3, Sb(OCH3)3, Sc(OiC3H7)3, Si(OC2H5)4, VO(OCH3)3, Yb(OiC3H7)3,Zn(OCH3)2, etc.
A conductive coating film is formed so as to cover conductive deposit, moreover so as to coat from conductive nanotube to conductive film. That is, the conductive nanotube and conductive film are electrically connected by the conductive coating film. And even in a case where the conductive film does not exist, the conductive coating film is utilized as an electrode film, by means of forming the coating film extended to the surface of a cantilever portion.
Accordingly, the coating film always exists, in any case either it is formed locally at a very small region, or extendedly over on a wide region. In the case of forming the coating film on the small region, the method to form a conductive deposit can be employed. In other words, in the case of the small region, a conductive coating film is formed by means of decomposing organic gases by an electron beam or an ion beam, and subsequently by means of heaping up locally the decomposed gases. On the other side, in the case of the wide region, various methods can be employed such as physical vapor deposition (PVD) or chemical vapor deposition (CVD), including vacuum vapor deposition, ion-plating, spattering, etc. and also such as electric plating or electroless plating, etc.
In a case where a conductive coating film is formed by coating a tip end and a tip end portion of a nanotube, the quality of its conductive substance is given to the probe needle of a nanotube. For example, in cases where strong magnetic metals such as Fe, Co, Ni, etc. are used as the conductive substances, the probe needle of the nanotube can detect the magnetic property of surfaces of specimens. Namely, this probe is able to function as the probe needle of a magnetic force microscope (MFM) which detects magnetic distribution of a specimen.
By approaching the probe for this conductive scanning type microscope to a specimen, in which the probe is coated with metal up to the tip end, and by applying a voltage between the specimen and the probe so that the specimen is cathode and the probe is anode, the metal of the tip end of a nanotube is ionized by the super-strong electric field which is induced between the tip end of the nanotube and the specimen. This metal ions are accelerated by the electric field to collide with the surface of the specimen and accumulate to form a metal deposit on the surface of the specimen. In this manner, the processes for specimen such as transposition and deposition of metallic ions, etc. can be performed by means of application of a voltage.
FIG. 1 is an outline diagram explaining first mode for a probe for a conductive scanning type microscope related to the present invention.
FIG. 2 is an outline diagram explaining second mode for a probe for a conductive scanning type microscope related to the present invention.
FIG. 3 is an outline diagram explaining third mode for a probe for a conductive scanning type microscope related to the present invention.
FIG. 4 is an outline diagram explaining fourth mode for a probe for a conductive scanning type microscope related to the present invention.
FIG. 5 is an outline diagram explaining fifth mode for a probe for a conductive scanning type microscope related to the present invention.
FIG. 6 is an outline diagram explaining sixth mode for a probe for a conductive scanning type microscope related to the present invention.
FIG. 7 is an outline diagram explaining a method, by which a small dot is formed by means of a probe for a conductive scanning type microscope related to the present invention.